In the disposition of Next Generation Network (NGN) and other Voice on IP (VoIP) networks, a Session Border Controller (SBC) is usually employed. The SBC may be disposed to the access layer of an NGN or a VoIP network for processing the VoIP call of all the users. It is a common method for protecting an NGN core network from being attacked by performing security control via the SBC. By performing a session control on the network border via the SBC, capabilities such as Quality of Service (QoS), call admission, and Network Address Translation (NAT) traversal may be provided for the whole VoIP network. The capability of the security control may also be provided via the SBC, so that the NGN core network may be protected from being directly attacked by a malicious user. A conventional method for controlling the security of the VoIP network border is implemented based on signaling and media proxy. The SBC is a processing device with a complex signaling protocol stack. During the resolving process of a packet, the packet to be resolved first needs to enter a protocol stack. When the packet has a defect, for example, if a cross circulation exists in the packet, the SBC may be broken down due to the malformed packet, so that the SBC may be attacked. Therefore, the main disadvantage of the existing SBC lies in that the security can not be ensured and is susceptible to be attacked by a malicious resource occupation.